Wet coils in HVAC systems, such as cooling coils, are susceptible to microbial growth because the wet surface of such coils provides excellent conditions (food source, moisture, ideal temperatures and humidity) for micro-organisms to grow. The microbial growth on such coils may have a negative impact on the indoor air quality as spores are released into the air stream. In addition, the microbial growth can give the indoor air an unpleasant smell. If not cleaned, the microbial growth can eventually block off the surface of the coil resulting in inadequate air flow, coil carryover and poor air handler performance. Because of this, it is common practice to have to clean heat transfer coils periodically to prevent such growth.